1. Technical Field
The present invention relates to a light source device equipped with a microwave electrodeless lamp emitting light by irradiating with a microwave and a projector equipped with the light source device.
2. Related Art
Projectors for projecting picture information or an image corresponding to a picture signal are frequently used for presentations or theaters. It is expected for a light source for these projectors to light quickly, to assure stable and high intensity, to be adjusted in the intensity without changing the emission spectrum, and, to have a long-life lamp for rapidly obtaining a bright projection picture. As such a light source, a light source device using a microwave electrodeless lamp has been proposed.
In the light source device using the microwave electrodeless lamp, a light flux and an intense electric field caused by the microwave coexist inside a microwave cavity in which the microwave electrodeless lamp is disposed. As a light source device, it is required to efficiently emit a light flux, and further prevent emission of the microwave energy in consideration of energy efficiency or safety.
Therefore, there is known a light source device having an electrodeless discharge lamp disposed inside a microwave cavity composed of a feeding opening from which a microwave is introduced, a cavity wall having an opening in at least a part thereof, and a meshed metal plate covering the opening, thus preventing emission of the microwave by the meshed metal section and transmitting the light flux through the opening sections of the meshed metal (see e.g., JP-A-58-194242, pp. 2, FIG. 2 (hereinafter Document 1).
Further, there is also known a microwave electrodeless discharge lamp device having a metallic tube member provided to a microwave resonator so as to project therefrom having one end opened inside the microwave resonator and the other end opened outside the microwave resonator, thus the tube member prevents emission of the microwave energy, and transmits a light flux emitted from the bulb (lamp) to lead the light flux outside the microwave resonator (see e.g., JP-A-2002-164188, pp. 4, FIGS. 1, 2 (hereinafter Document 2)).
According to the Document 1 described above, since there is a light flux reflected by the meshed metal section, a problem of deterioration of the light efficiency arises. Further, it is projected that the meshed metal is heated by the heat radiation from the electrodeless discharge lamp, thus the structural strength of the meshed metal is weakened.
Further, according to the Document 2, the length of the tube member necessary for preventing emission of the microwave is defined to be six times as large as the cross-sectional area of the opening section of the tube member. By increasing the length of the tube member, there arises a problem of increasing the optical, loss in the tube member to decrease the light efficiency.